;+
; NAME:
;       BITGET
;
; PURPOSE:
;
;       Returns the bit value (0 or 1) of a specified bit in a supplied number.
;
; AUTHOR:
;
;       FANNING SOFTWARE CONSULTING
;       David Fanning, Ph.D.
;       1645 Sheely Drive
;       Fort Collins, CO 80526 USA
;       Phone: 970-221-0438
;       E-mail: davidf@dfanning.com
;       Coyote's Guide to IDL Programming: http://www.dfanning.com
;
; CATEGORY:

;       Utilities
;
; CALLING SEQUENCE:
;
;       bitValue = BitGet(number, bit)
;
; INPUT_PARAMETERS:
;
;       number:          The input number. Should be a scalar integer. If not, it is converted to
;                        one by rounding.
;
;       bit:             The number of the bit you are interested in. A value between 0 and 63.
;                        If not supplied, all 64 bit values of the number are returned. May be
;                        an array of bit numbers.
;
; OUTPUT_PARAMETERS:
;
;      bitValue:        The value, 0 or 1, of the specified bit in the number.
;
; KEYWORDS:
;
;     SILENT:           If set, suppresses informational messages regarding rounding operations.
;
; MODIFICATION HISTORY:
;
;       Written by David W. Fanning, 14 June 2006.
;-
;******************************************************************************************;
;  Copyright (c) 2008, by Fanning Software Consulting, Inc.                                ;
;  All rights reserved.                                                                    ;
;                                                                                          ;
;  Redistribution and use in source and binary forms, with or without                      ;
;  modification, are permitted provided that the following conditions are met:             ;
;                                                                                          ;
;      * Redistributions of source code must retain the above copyright                    ;
;        notice, this list of conditions and the following disclaimer.                     ;
;      * Redistributions in binary form must reproduce the above copyright                 ;
;        notice, this list of conditions and the following disclaimer in the               ;
;        documentation and/or other materials provided with the distribution.              ;
;      * Neither the name of Fanning Software Consulting, Inc. nor the names of its        ;
;        contributors may be used to endorse or promote products derived from this         ;
;        software without specific prior written permission.                               ;
;                                                                                          ;
;  THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY        ;
;  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES    ;
;  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT     ;
;  SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT,             ;
;  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED    ;
;  TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;         ;
;  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND             ;
;  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT              ;
;  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS           ;
;  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.                            ;
;******************************************************************************************;
FUNCTION BitGet, value, bit, SILENT=silent

   ; Return to caller if something goes wrong.
   On_Error, 2

   ; Get the data type.
   theType = Size(value, /TYPE)

   ; Special pointer processing.
   IF theType EQ 10 THEN BEGIN
      theValue = *value
      theType = Size(theValue, /TYPE)
   ENDIF ELSE theValue = value

   ; Validate data type. Round any non-integer data type.
   CASE 1 OF
      theType LT 1: Message, 'VALUE must be defined.'
      theType GT 0 AND theType LT 4:
      theType GT 5 AND theType LT 10: Message, 'Wrong data type (' + Size(theValue, /TNAME) + $
         ') supplied for determining bit value.'
      theType EQ 11: Message, 'Wrong data type supplied for determining bit value.'
      theType GT 11 AND theType LT 16:
      ELSE: BEGIN
         IF ~Keyword_Set(silent) THEN Message, 'Converting value to INTEGER format...', /Informational
         theValue = Round(theValue, /L64)
         END
   ENDCASE

  ; Make sure the value is scalar.
  IF N_Elements(theValue) NE 1 THEN Message, 'Examined value must be a scalar.'
  theValue = theValue[0]

  exponent = 2ULL^UL64indgen(64)

  ; If not bit value is specifed, return all the bits in the value.
  IF N_Elements(bit) EQ 0 THEN BEGIN
      CASE 1 OF
         theType EQ 1: RETURN, Reverse(((theValue AND exponent)/exponent)[0:7])
         theType EQ 2 OR theType EQ 12: RETURN, Reverse(((theValue AND exponent)/exponent)[0:15])
         theType EQ 3 OR theType EQ 13: RETURN, Reverse(((theValue AND exponent)/exponent)[0:31])
         ELSE: RETURN, Reverse((theValue AND exponent)/exponent)
      ENDCASE
  ENDIF ELSE  bit = 0 > bit < 63 ; Confine it to correct range.

  ; Calculate the bit value and return it.
  RETURN, ((theValue AND exponent)/exponent)[bit]

END